I need to express mail something, but just cannot do it because there is no mailing address other than a PO Box one. Do you know where and how I can obtain a directory for PO boxes in a certain city and state that provides each box number a stree address?

I don't think you want the street address where the box is. That could be on the other end of town (or even in another city) from where the recipient resides or does business. You cannot get a receipt that way. Try google-searching whoever it is you actually want to send the mail to, or call them up and ask for the street address where they are actually located.